Allyl alcohol-styrene copolymers



Patented Mar. 3, 1953 -UNl-TED "STATES ALLYL ALCOHOL-STYRENE COPOLYMERSEdward C. Shokal, Walnut Creek, and Paul A. Devlin, San Francisco,Calif., assignors to Shell Development Company, San Francisco, Calif., acorporation of Delaware No Drawing. Original application April 5, 1948,

Serial No. 19,176.

Divided and this application October 23, 1951, Serial No. 252,796

6 Claims.

This invention relates to the products obtained by copolymerizingstyrene with allyl alcohol in the presence of dispersed oxygen ascatalyst, and to unsaturated fatty acid esters of such products.

There has been a long standing need for sur-- face coating compositionscapable of drying and setting hard in short periods of time. The speedrequired in modern industrial manufacture has substantially precludeduse of paints containing linseed oil as the primary drying constituentbecause such paints dry too slowly. Rapid drying nitrocellulose lacquerswere developed which dry by evaporation of volatile solvents so as toleave a film of nitrocellulose, but the resulting film is lacking inmany qualities of durability. Compositions containing variousresin-forming materials which set rapidly by baking have foundconsiderable use. However, the necessity of baking such finishes atelevated temperatures is a serious disadvantage which also addsmaterially to the cost. The real solution of the problem lies insecuring a drying oil which is capable of air drying rapidly 'to a hardfilm at ordinary temperatures without baking, which film must also havequalities of durability such as are possessed by dried linseed oil, forexample.

The drying oil acid esters of polyallyl alcohol having at least fivehydroxyl groups per molecule are faster drying than the correspondingunsaturated glycerides, it being shown in U. S. Pat- .ent 2,378,827,that this result is due to the fact that such polyallyl esters contain agreater number of unsaturated acyl groups than are present in theglycerides. In View of this disclosure especially, it was surprising todiscover that by copolymerizing styrene with allyl alcohol in thepresence of dispersed oxygen as catalyst there was obtained a copolymerwhich, although it contained only about 3'01 4 hydroxyl groups permolecule, gave drying'oil acid ester that was substantially fasterdrying thanlthe corresponding drying oil acid ester of homopolymericallyl alcohol having five or more hydroxyl groups per molecule. Besidesdrying and setting hard at normal temperatures Without baking in suchshort periods as from a few minutes to about an hours time, the newsynthetic drying oils of the present invention gave films havingexcellent durability. The new. oils thus supply the need forsatisfactory material having very fast drying properties. However, inorder to obtain the desired properties for the'drying ester, thecopolymer is required to be prepared in a particular manner. p

The process forpreparing the drying oil comprises the heating of aliquid mixture of polymerizable compounds consisting only of allylalcohol and styrene while bubbling or dispersing molecular oxygentherethrough at a temperature of about 100 C. to 200 0., andsubsequently esterifying substantially completely the resultingcopolymer of allyl alcohol and styrene with unsaturated higher fattyacid, i. e., esterifying until the acid number of the oil is reduced toless than about 30. In order that the drying ester will have the desiredsuperiority in rate of drying, it is necessary that the copolymercontain proportions of combined styrene within a particular range. Thecopolymer of the invention contains at least 30% by weight of combinedstyrene. While the copolymer contains at least 30% of combined styrenein order to realize the rapid rate of drying for the unsaturated fattyacid ester therefrom, too high a percentage of styrene results in esterswhich have viscosities too high to be practicable. Consequently, it isdesirable to use a copolymer containing not more than combined styrene.While copolymers having percentages of styrene at the outer portions ofthis 30% to 80% range can be used for preparation of thedrying esters,the properties of drying esters from copolymers containing about 35% to60% of combined styrene are so much more superior, that this narrowerrange is preferred. The best drying esters of the invention are thosefrom the copolymer of allyl alcohol and styrene containing about 50% ofcombined styrene in the copolymer.

The copolymer needed for preparation of the drying ester is produced byheating a mixture of allyl alcohol and styrene for about 2 to 10 hoursat C. to 200 C. while bubbling a slow stream of gaseous oxygen throughthe mixture. Since the copolymerization requires the oxygen to bebrought into intimate contact with a liquid mixture of the compounds,and since the temperature of operation is above the boiling point of atleast allyl alcohol, superatmospheric pressure sufficiently high tomaintain the mixture in liquid phase is employed. Preferably, a pressureof 150 to 400 pounds per square inch of pressure is used especially whenemploying the preferred temperature of C. to C. By efiecting thecopolymerization in a closed pressure vessel or bomb which is fittedwith a gas release valve set at the operating pressure, the contents inthe reaction vessel are easily maintained at the desired pressure bypumping gaseous oxygen into the bomb in such a manner that the gaseousoxygen bubbles through the liquid contents thereof. The amount ofgaseous oxygen bubbled through the mixture may be varied over widelimits with little difference in effect other than increasing the rateof polymerization somewhat with the corresponding amounts of oxygen. Theefliciency of the copolymerization is aided by using an elongatedreaction vessel in which the oxygen is introduced in the bottom thereofthrough a spray nozzle hav-- ing many openings so as to produce a largenumher of small oxygen bubbles. Ordinarily at least two volumes ofoxygen (S. T. P.) per volume of liquid mixture of polymerizablecompounds per hour are used. This rate can be increased at 2t volumes or200 volumes of oxygen if desired and may also be less than 2 volumes,although the rate of copolymerization will be slow below such an amountof oxygen. However, the presence of oxygen is essential to formation ofthe desired copoiymer since merely heating the mixture of styrene andallyl alcohol in the absence of oxygen results in formation ofhomopolymeric styrene Without appreciable copolymerization of the allylalcohol therewith. While pure oxygen may be used as the catalyst, air isordinarily preferred for reasons of economy. If desired, oxygen dilutedwith inert gas such as carbon dioxide, methane or nitrogen may be used.

The proportions of styrene and allyl alcohol used in the mixture ofcopolymerizable compounds are chosen so as to obtain a copolymercontaining the desired percentage of combined styrene. In effecting theprocess of the invention it was found that the percentage of styrenecontained in the resulting copolymer does not correspond to thepercentage contained in the monomer mixture from which the copolymer isformed. Apparently this result is caused by the much greater speed ofthe copolymerizing reaction of the styrene than that of the allyl a1-cohol. Thus, a starting liquid mixture of allyl alcohol containing aboutby Wei ht of styrene produces a copolymer containing about 30% ofstyrene when the copolymerization is conducted until there is a 20% to40% conversion to copolymer which is usual. If the starting mix ture ofallyl alcohol contains about 40% of styrene the resulting copolymer willcontain about 80% of combined styrene. Consequently, in order to obtainthe copolymer containing 30% to 80% of combined styrene, there is used amixture of allyl alcohol containing 10% to 40% of styrene. In order tosecure the much more preferred copolymer containing 35% to 60% combinedstyrene, a monomer mixture is used consisting of allyl alcohol and to25% styrene. The best copolymer is secured from a starting mixtureconsisting of about 80% allyl alcohol and styrene.

The amounts of monomers copolymerizing may be better controlled bycontinuously or intermittently introducing styrene into the reactionmixture during the copolymerization. This expedient enables a copolymerto be obtained having a more uniform composition and is thus a desirablemanner of operation in executing the process of the invention.

Owing to the rather severe conditions which are necessary to effect thecopolymerization of the allyl alcohol with the styrene, there is anappreciable destruction of hydroxyl groups contained in the combinedallyl alcohol of the copolymer. Consequently, the novel copolymcr of theinvention does not contain as many hydroxyl groups per molecule as wouldbe expected from the proportion of combined styrene in the co polymer.The copolymer having about 30% to 80% of combined styrene contains about50% to 60% of the theoretical hydroxyl groups which would be expected.However, in spite of the fact that there should be fewerhydroxyl groupsper molecule with corresponding proportions of combined styrene, andeven though the copolymer does not contain the theoretical number ofhy-- yl roups, it-was found that the copolymer of the inventioncontainsan av rag of about 3 to 4 hydroxyl groups per moleculeregardless of the percentage of combined styrene in the copolymer whenit contains from about 30% to combined styrene. The copolymer havingthis advantageous and unexpected property is a brittle solid at roomtemperature which does not change to an infusible material upon furtherheating with or without the presence of a polymerization catalyst. Theproperties of being fusible permit preparation therefrom of the dryingesters, which preparation would be impossible if the copolymer becameinfusible.

The drying esters of the invention are prepared by esterifying thecopolymer with the unsaturated fatty acids. In order to effect the desired esterification, about equivalent quantities of the copolymer andunsaturated fatty acid are mixed and heated at about 170 C. to 250 C. inan inert atmosphere and the formed water of esterification is allowed todistill therefrom. By equivalent quantities of the copolymer andunsaturated fatty acid, reference is made to stoichiometric proportionssuch that there is about one hydroxyl group for each carboxylic acidgroup present in the initial mixture. Thus, for example, in esterifyinga copolymer having a hydroxyl value of 0.55 equivalent of hydroxyl pergrams with unsaturated fatty acids from linseed oil having an acidnumber of about 199 (equivalent weight=282), there is used about partsby weight of acid for each 100 parts by weight of the copolymer. The useof excess acid is ordinarily to be avoided. In some cases it may,however, be desirable to have present about 10% to 20% excess ofcopolymer. The esterification is conveniently efiected in a, kettlefitted with a stirrer and distilling column. An inert gas such as carbondioxide or nitrogen is bubbled through the esterifying mass at a slowrate to aid in removal of the water. The heating is continued until theesterification is substantially complete, which fact may be readilyascertained by determining the acid number of the reaction mixture. Theesterification is continued until the acid number is reduced to about 30or less.

In preparing the synthetic drying oil there may be used any of theunsaturated fatty acids of 12 to 20 carbon atoms having an iodine numberof 85 or higher. While an ester having drying properties may be preparedfrom fatty acids containing a single olefinic bond such as, for example,oleic acid, lauroleic acid, palmitoleic acid, or gadoleic acid, it ispreferable to employ a more higher unsaturated fatty acid such aslinoleic or linolenic acid. Particularly suited are the drying oil fattyacids obtained as a mixture of individual acids by hydrolysis of naturaldrying oil such as linseed oil, soya bean oil, dehydrated castor oil,perilla oil and the like. Also the unsaturated fatty acids obtained bytreating drying oils so as to effect conjugation of the double bonds asby alkali isomerization are very suitable for preparation of thesynthetic drying esters of the invention.

In effecting the esterification, especially with drying oil fatty acids,care is needed to avoid over-heating or unduly prolonging the heatingafter substantially complete esterification because the formed esterwill body and eventually gel. It is sometimes advantageous to deter or'prevent the danger of gelling by effecting the esterification with fromabout 10% to 50% of kerosene present in the reaction mixture. Y

It is at times desirable to modify the synthetic drying oil by effectingthe esterification with a mixture of the unsaturated fatty acid and adicarboxylic acid or anhydride such as maleic anhydride, phthalicanhydride, fumaric acid, sebacic acid, succinic acid, etc. When adicarboxylic acid is used in conjunction with the unsaturated fattyacids, the proportions of the acids are adjusted so there is about oneequivalent of the mixed fatty acid and dicarboxylic acid per hydroxylequivalent of the copolymer. Ordinarily, up to about 50% by weight ofdicarboxylic acid in the mixture of acids are used. If desired otherpolyhydric alcohols may be used in admixture with the copolymer informing the ester such as glycerin, ethylene glycol, diethylene glycol,pentaerythritol, dipentaerythritol, etc.

For the purpose of illustrating the invention in greater detail, thefollowing examples are given.

Example I Copolymerization of styrene and allyl alcohol was effected ina one-liter nickel-lined pressure bomb equipped with a stirrer andfitted with a stainless steel tube enabling air to be bubbled throughthe liquid contents of the bomb. The bomb was charged with about 635grams of material consisting of of styrene and 90% of allyl alcohol. Thecopolymerization was effected at about 125 C. i 5 C. in a 4 hour periodduring which air was continuously bubbled through at such a rate thatthe total exit gas amounted to about 6.7 cu. ft. (S. T. P.). Thepressure in the bomb during the copolymerization was 260 pounds persquare inch. The treatment gave a crude liquid mixture weighing about647 grams. The product was subjected to rapid distillation at 1 mm.pressure up to a temperature of about 110 C. The amount of copolymerrecovered indicated a conversion of about 25%. A material balance showedthat the copolymer contained about 38% of combined styrene. Themolecular weight was 479. Analysis showed the hydroxyl value of thecopolymer to be 0.55 equivalents of hydroxyl per 100 grams. Thisindicates an average of about 2.6 hydroxyl groups per molecule.

Example II The copolymer prepared as described in Example I wasesterified with linseed oil fatty acids. About 10.2 parts by weight ofthe copolymer were dissolved in 15.7 parts of linseed fatty acids in adistilling vessel. The reaction mixture was blanketed with an atmosphereof carbon dioxide and heated to 230 C. during one-half hours time. Thetemperature was maintained at 230 C. for a total time of 6 hours whilebubbling a slow stream of carbon dioxide through the re action mixture.During this time, the reaction mixture remained clear and homogeneous.The acid number of the reaction mixture was determined at intervals withthe following results:

Hours heating at 230 0. Acid No.

no 95 3 Hanan drying ester. The solution was then aged for 24 hours. Theaged solution was applied to a plate glass panel with a doctor bladehaving a clearance of 0.005 inch. The panel was dried in a cabinetwherein air circulated at 25 C. and 50% relative humidity.

Frequent observations were made of the drying film and the times werenoted for three tests of drying and hardening. The first of these wasthe time required for the film to set to touch. The film was set totouch when it did not adhere to the finger after application of gentlepressure. The film was considered dried hard when, after squeezing thepanel between" the thumb and, forefinger, no movement of the film wasnoticeable nor any imprint of the finger was observable. The final, mostsevere test of hardness and dryness was the time when the film becamecottonfree. A film was deemed cotton-free when, upon being forcefullydabbed with a wad of absorbent cotton, no cotton fibers adhered to thefilm. The cotton-free test is very severe since the film must havecompletely hardened so that no minute areas remain having any residualstickiness or softness. Some paints and varnishes containing inferioringredients never do harden sufficiently to pass this test even monthsafter application. Further details of these drying tests will be foundin the book of Henry A. Gardner Physical and Chemical Examination ofPaints, varnishes, Lacquers and Colors, 1939, pp. 106-l0'7.

The film of the synthetic drying oil prepared and dried as describedabove was found to set to touch in only 80 minutes, to have dried hardin 3 hours an 40 minutes, and become cotton-free in 6 hours and 15minutes. In comparison, a film from linseed oil prepared in the same wayand dried under identical conditions set to touch in 3 hours and 30minutes, dried hard in 12 hours, but had still not become cotton-freeafter 30 days time.

The Sward hardness of the film from the synthetic drying oil measured asfollows: 9 after one week; 10 after two weeks; 12 after four weeks. Thelinseed oil film gave a Sward hardness of 2 after one week, and remainedthe same after two and four weeks.

In order to test the durability of the dried film of the syntheticdrying ester, it was subjected to a water-resistance test. When filmsare immersed in cold or boiling water they may have a tendency to losetheir glossiness and become dull. The dulling tests were conducted inthe following manner. The 50% solution of drying oil described above wasflowed on tinned steel panels. The effect of contact with cold water wasdetermined by allowing the'coated panel to dry at room temperature for10 days after which the panel was immersed half way in water for 10days. The panel was then removed and the degree of dulling was observedto be moderate. Ester films of good quality tend to recover theirglossiness after removal from contact with water. The coated panel ofthe synthetic drying oil was observed 3 days after removal from thewater and it was found that the dulling was only slight at that time.

The effect of boiling water was determined by drying a coated panel forone week, after which it was immersed half way in boiling distilledwater for 15 minutes. This caused no dulling of the film} Observation ofthe extent of recovery 3 days later, of course, also showed no dullingand the same glossiness as before immersion in the boiling water.

Whenpanels coated in the-same Way with a film from linseed oil weresubjected to the-same tests it was found that the dulling of the filmafter removal from the cold water was very heavy and the recovery 3 dayslater showed the degree of dulling to still be heavy. A panel coatedwith a dried film from linseed oil showed very heavy dul-ling in theboiling water test although the recovery 3 days later resulted in thefilm having only moderate dulling.

The fast drying qualities of the drying oil acid esters of the inventionand the excellent durability of the dried films thereof are evident fromthe foregoing findings and comparisons with linseed oil which is arecognized standard drying oil.

The rapid drying qualities of the esters of the invention are furtherillustrated by the results summarized in the table below. The polymerswere prepared in the same manner as described in Example I and forpurposes of comparison there was used varying proportions of styrene andallyl alcohol including allyl alcohol alone. The homopolymeric allylalcohol and the copolymers of allyl alcohol and styrene were thenesterified substantially completely with the mixtures of fatty acidsobtainable by hydrolysis from linseed oil, the esterification beingeiiected in the same manner as described in Example II. The syntheticdrying oils were tested for drying qualities and hardness of theresulting film.

2. A. process of producing a copolymer of allyl alcohol and styrenesuitable for use in preparing drying esters, therefrom which comprisesheating a liquid mixture of polymerizable compounds consisting of allylalcohol and to styrene at 120 C. to 150 C. While bubbling oxygentherethrough under a. pressure of 150 to 400 pounds per square inch.

3. A process of producing a copolymer of allyl alcohol and styrenesuitable for use in preparing drying esters therefrom which comprisesheating a liquid mixture of polymerizable compounds consisting of allylalcohol and about 20% styrene at about 125 C. While bubbling airtherethrough under a pressure of 260 pounds per square inch.

4-. A copolymer of allyl alcohol and styrene suitable for use inpreparing drying esters there from, said copolymer containing to 80% ofcombined styrene and obtained by heating a liquid mixture ofpolymerizable compounds consisting of allyl alcohol and styrene at 100C. to 200 C. while bubbling oxygen therethrough.

5. A copolymer of allyl alcohol and styrene suitable for use inpreparing drying esters therefrom, said copolymer containing to ofcombined styrene and obtained by heating a liquid mixture ofpolymerizable compounds consisting of allyl alcohol and styrene at C. to200 C. while bubbling oxygen therethrough.

6. A copolymer of allyl alcohol and styrene Percent Styrene Linseed OilFatty Acid Ester of Polymer I i Polymer 1 03 Val, Drying Time (Mid)Sward Hardness f eq 100 Mid Gardnerh ed Polymer grams liioldt q l D isc.25 2? gfg 2528 1 Week 2Wcelcs' 4 Weeks i 0 0 0. s7 9. 6 v 9.5 360 9 s1.0

5 23 0. 58 9. l Z3-Z4 85 230 270 12 in,

l 10 3i 0. 69 12. 6 Z1 60 270 ll l4 14 20 52 O. 37 19. 6 Z8 60 i l5 1821 40 80 0. 21 15. 7 Zl0 10 180 150 18 l9 18 Linseed Oil 210 720 30 days2 2 2 The above table shows the superior rate of drying possessed by theesters of the invention in comparison to the corresponding drying estersof homopolymeric allyl alcohol or linseed oil. Furthermore, theresulting dried films are harder for the esters from the copolymer thanthose from the homopolymer or from linseed oil.

This application is a division of our copending application Serial No.19,176, filed April 5, 1948, now U. S. Patent 2,588,890.

We claim as our invention:

1. A process of producing a copolymer of allyl alcohol and styrenesuitable for use in preparing drying esters therefrom which comprisesheating a liquid mixture of polymeriz l compounds consisting of allylalcohol and 10% to 40% styrene at 100 C. to 200 C. while bubbling oxygentherethrough.

suitable for use in preparing drying esters therefrom, said copolymercontaining about 50% of combined styrene and obtained by heating aliquid mixture of polymerizable compounds consisting of allyl alcoholand about 20% styrene at about 125 C. While bubbling air therethroughunder a pressure of about 260 pounds per square inch.

EDWARD C. SHOKAL. PAUL A. DEVLIN.

REFERENCES CITED UNITED STATES PATENTS Name Date Shokal Mar. 11, 1952Number

4. A COPOLYMER OF ALLYL ALCOHOL AND STYRENE SUITABLE FOR USE INPREPARING DRYING ESTERS THEREFROM, SAID COPOLYMER CONTAINING 30% TO 80%OF COMBINED STYRENE AND OBTAINED BY HEATING A LIQUID MIXTURE OFPOLYMERIZABLE COMPOUNDS CONSISTING OF ALLYL ALCOHOL AND STYRENE AT 100*C. TO 200* C. WHILE BUBBLING OXYGEN THERETHROUGH.